1. Field of the Invention
This invention relates to altering the temperature and humidity of gases used to inflate body cavities prior to and during medical procedures. More specifically, it relates to apparatus for, and method of, heating, humidifying and filtering insufflation gases prior to passage of the gases into the patient.
Two applications for this apparatus are for laparoscopic and endoscopic procedures, however this application may relate to other procedures which involve the inflation or supply of gas to the patient.
2. Summary of the Prior Art
Endoscopic procedures are minimally invasive procedures which enable a body cavity to be visualized by inserting surgical instruments through natural openings or small punctures. Endoscopy is used to visualize most areas of the human body such as, gastrointestinal, circulatory, respiratory, auditory, urinary, reproductive, nervous, ocular and musculoskelital systems.
A body cavity may be visualised by inserting the endoscope through the natural opening, however, some cavities are not able to be entered in this manner due to the cavity being located in the body without a natural opening thus incisions must be made to visualise the cavity. Laparoscopy and thoracoscopy are examples of making small punctures to visualise the body cavity. Upper and lower Gastrointestinal (GI) endoscopy and bronchoscopy are examples of making use of natural orifices to visualise the body cavity.
Most operative laparoscopic procedures begin by creating a viewing and working space inside the peritoneal cavity of a patient to facilitate laparoscopic visualisation and safe, effective instrument manipulation. This intra-abdominal space is typically created and maintained using an insufflator (an adjustable throttling pressure regulator and flow controller), which delivers gas, usually carbon dioxide (CO2) into the peritoneal space, distending the abdominal wall.
There are two ways to introduce gas to the peritoneal cavity. In the first method, an incision may be made in the abdominal wall and a cannula, the instrument through which the abdomen is inflated, is inserted in the incision. In the second method, a needle (for example, a Verres needle) which is attached to a flexible tube connected to an insufflator, is inserted into the peritoneum cavity. Later the needle is withdrawn and a cannula is introduced to the cavity by puncturing the abdominal wall with a trocar. In the second method the abdomen is inflated before insertion of the cannula. In both cases, the tubing from the insufflator is connected to the cannula, and the gas flow from the insufflator is increased to maintain the pneumoperitoneum, the space within the abdomen. After initial insufflation and insertion of a laparoscope through the primary cannula, additional cannulas are placed in the abdomen under laparoscopic observation. At the end of the operating procedure, all instruments and cannulas are removed from the pneumoperitoneum, the gas is expelled, and each incision is closed. For thoracoscopy a similar procedure is followed.
Colonoscopy and sigmoidoscopy are procedures to visualise the lower GI tract by entry into the rectum. Gastroscopy and bronchoscopy are procedures to visualise the upper GI tract and the parts of the lungs through entry into the mouth. These procedures are carried out in similar ways. Most endoscopic procedures begin by creating a viewing and working space inside the body cavity of a patient to facilitate endoscopic visualisation and safe, effective instrument manipulation. The endoscope is inserted into the cavity and visibility is usually assisted by insertion of gas which may be air or CO2. The quantity and flow of gas may be controlled by the clinician performing the examination or by the equipment.
While the importance and use of temperature and moisture conditioning of respiratory gases is known, until recently little attention had been given to the temperature and/or humidity condition of gases used to create a pneumoperitoneum or any other gas filled cavity.
Currently, most endoscopic equipment does not heat and humidify the air. An endoscope cable provides both optics and air as well as fluid to the body cavity and thus due to the lack of connections, lack of available space within the cable and the current cable design, it is difficult to heat the fluid and/or air used in these procedures. Usually a cavity is made within the part of the body that is used as a space to manipulate apparatus during the surgery. Dry gas and unheated fluids supplied to the body during an endoscopic procedure can lead to drying of exposed tissue and to the possibility of adverse effects such as cell death and adhesions.
In general, only a small number of insufflators, which are used for surgery in abdominal cavities, are produced today which control the temperature of the gas, and which also humidify the gas. When the insufflator provides gas flows of various magnitudes, typically 1 to 10 liters per minute, it must reduce the pressure of the gas from the CO, cylinder, that being about 57 atmospheres, to approximately 1 atmosphere. Such a process is called “throttling”, which causes the gas to be cooled via a thermodynamic process known as Joule Thompson cooling. With CO, as the insufflation gas, Joule Thompson cooling can reduce the gas temperature as much as 50° C. to 70° C., depending on gas mass flow rates. The large difference in heat capacities of the insufflator metal hardware and the CO, gas stream permits the gas stream to be reheated to approximately operating room ambient temperature, approximately 20° C., before the gas enters the patient. In the case of large gas flows, this unplanned and uncontrolled reheating effect could be incomplete and the insufflator gas could leave the insufflator apparatus at temperatures considerably less than the ambient temperature of approximately 20° C. In any case, insufflator gas cannot reach a temperature higher than this ambient temperature, and hence, the insufflator gas enters the patient at a temperature substantially less, at least 17° C. less, than the patient's physiological core of approximately 37° C.
Newly developed insufflators and ancillary devices have recognized this problem and have attempted to correct it by adding heat to the gas stream before it enters the delivery system which directs the gas to the cannulas. This method is thermodynamically unsound because it fails to recognize the thermal capacity mismatch between the flowing gas stream and the gas delivery system between the insufflator and the trocar incision point in the cavity even when the delivery system is only 6 to 10 feet of polymer tubing. In addition, this method overlooks the above heat transfer that occurs between the gas stream and the ambient temperature gas delivery tubing. Because of these thermal conditions, the temperature of any gas preheated at or in the insufflator itself will return to approximately the ambient temperature after flowing as little as 4 feet after leaving the insufflator.
U.S. Pat. No. 5,006,109 (Douglas et al.) relocates the temperature sensor to the point of gas administration, but this relocation does not solve this problem, because as has been mentioned above, that point can be, in practice, 6 to 10 feet from any temperature controller. Such an arrangement leads, with the low flow rates typically used in these surgical methods, to “transportation lags” which render stable feedback control difficult to achieve under major rapid flow rate changes which are typically required by these endoscopic and laparoscopic surgical procedures. Thus, the gas reaches the patient at a temperature much lower than the desirable 36° C. to 38° C.
Insufflation gases typically are delivered extremely dry. The extreme lack of moisture in the insufflation gas can lead to drying of exposed surface tissue of the cavity and to the possibility of adhesion formation within the cavity. Also, it was recognised that the lack of moisture could lead to hypothermia.
U.S. Pat. No. 5,411,474 (Ott et al.) discloses an apparatus for treating gas prior to the use of the gas in a medical procedure involving a patient. The gas is received into a humidifier from an insufflator, and the gas exists the humidifier and enters the patient via tubing.
U.S. Pat. No. 6,068,609 (Ott et al.) further discloses an apparatus and method for providing heated and humidified gas to a patient such that heat loss in transfer of the gas is minimized, and such that humidity of the gas is monitored and the temperature of the gas is controlled throughout the procedure.
In both the abovementioned U.S. patents in the case of laparoscopic procedures the humidifier is connected to the cannula and is thus, proximal to the patient at the trocar incision point in the patient's abdomen. This means the humidifier is within the “operating sterile zone” as the surgeon will be required to touch the humidifier as he/she moves the cannula during the operation to manoeuvre instruments within the abdomen. Therefore, the humidifier must be easily sterilised and capable of maintaining sterilisation. Furthermore, with the humidifier being located close to the patient, the surgeon may experience obstruction difficulties during the operating procedure that may restrict the movement of the surgeon or instruments in this already crowded space. The surgeon may experience increased fatigue when holding or moving the instruments through the cannula that has the humidifier attached to it. Obstruction difficulties may increase the operation time, and the weight of the humidifier at the incision area may cause bruising and tissue damage, such as tearing, leading to the possibility of increased pain and recovery time of the patient/Furthermore, the humidifier may cause pressure sores or thermal injury proximal to the incision.